Long-term excessive alcohol consumption is the leading cause of illness and death from liver disease in the United States. The number of people with alcoholic liver disease is conservatively estimated at over two million. Despite extensive research, the mechanisms of ethanol-induced hepatotoxicity remain unclear. Previous studies from this laboratory have shown that chronic ethanol consumption impairs vital hepatic functions, including hepatocyte-extracellular matrix (ECM) interactions, selective for the perivenous (PV) region of the liver, where alcoholic liver injury starts and predominates. These ethanol-induced defects include 1) impaired hepatocyte attachment to and spreading on various matrix substrates and 2) increased expression and association of integrins, the major ECM receptors in hepatocytes, with the actin cytoskeleton. [unreadable] These intracellular and extracellular impairments elicited by ethanol suggest impaired actin cytoskeleton remodeling, possibly due to dysregulated activation of rho family GTPases, which could adversely affect fundamental hepatic functions like regeneration, liver specific gene expression and protein trafficking and lead to liver injury. Preliminary data from this laboratory show the activation of rac (the rho family GTPase that induces cell spreading) is impaired in PV hepatocytes after chronic ethanol administration. This impairment, along with altered activation of the other two rho family GTPases, Cdc42 and RhoA, may be responsible for the ethanol-induced defects observed previously by this laboratory. Additional preliminary data show that treatment of cultured PV hepatocytes with the bioactive phospholipid, lysophosphatidic acid (LPA), reverses the ethanol-induced spreading defect. LPA has been shown to regulate rac, Cdc42 and RhoA activation to initiate cytoskeletal remodeling and thus promote optimal cell-ECM interactions. These interactions ultimately mediate various signal transduction pathways to promote proper cell function. Therefore, this proposal will study ethanol-induced defects in rho family GTPase activation and determine the mechanism(s) of the LPA-induced reversal of the ethanol-induced spreading defect. Heavy alcohol consumption can impair vital hepatocyte functions, leading to liver cirrhosis and death. Our studies have begun to characterize how alcohol impairs these functions. Thus, results from the proposed research could lead to effective treatment strategies in alcoholic liver disease. [unreadable] [unreadable] [unreadable]